Magnetic head with saturable gap and matrix device comprising a multiplicity of such heads

Abstract

A magnetic head employs a gap of magnetic material between two poles. The magnetic material of the gap has a saturation value less than the saturation value of the poles. When the gap material is not saturated, the magnetic field remains contained within this gap.

We claim: 
     
       1. A matrix magnetic head device comprising: a plurality of magnetic heads;   conductors associated with each of said plurality of magnetic heads and extending in rows and columns for producing a magnetic field within the magnetic heads when an excitation current flows through the conductors;   wherein each of the magnetic heads comprises two magnetic poles separated by a gap comprising a magnetic material having a saturation value less than a saturation value of the poles, the gap being saturated only at a predetermined threshold first intensity of excitation current and the poles being saturated at a predetermined threshold second intensity of excitation current which is substantially equal to three times that of the first intensity, such that when the gap is not saturated, the magnetic field remains confined within the gap.   
     
     
       2. A device according to claim 1, wherein the material of the gap is a ferrite. 
     
     
       3. A device according to claim 1, wherein the material of the gap is an alloy of iron, aluminum and silicon. 
     
     
       4. A device according to claim 3, wherein the material constituting the poles is an alloy of iron, aluminum and silicon with an aluminum content less than that of the gap material. 
     
     
       5. A device according to any of claims 1, 2 or 3, wherein the poles consist of the same material as the gap material and wherein a depth of the gap is smaller than a depth of the poles. 
     
     
       6. A device according to claim 1, further comprising a layer of material having a reluctance far greater than that of the poles and the gap when the gap material is not saturated. 
     
     
       7. A device according to claim 6, wherein the layer of material comprises a nonmagnetic material. 
     
     
       8. A device according to claim 7, wherein the layer of nonmagnetic material is situated adjacent the poles. 
     
     
       9. A matrix magnetic head device comprising: a plurality of magnetic heads;   conductors extending in rows and columns for carrying an excitation current which produces a magnetic field within said plurality magnetic heads, wherein each intersection of a row conductor and a column conductor is associated with each magnetic head;   wherein each of the magnetic heads comprises a pair of poles separated by a gap comprising a magnetic material having a saturation value less than a saturation value of the poles, a saturation of the gap of each head occurring when a sum of intensities of the excitation currents in the row and column conductors associated with each head attains a first intensity value, and the saturation of the poles of each head occurring when of the sum of intensities attains a second intensity value, the second value being about three times the first value, such that when the gap is not saturated the magnetic field remains confined within the gap.   
     
     
       10. A matrix device according to claim 9, further comprising a substrate of magnetic material from which blocks project, wherein the poles and the gap are situated on the ends of the blocks. 
     
     
       11. A matrix device according to claim 9, wherein, when recording data, the row conductors are addressed by successive current pulses of opposite polarities, an absolute value of each current pulse being about double the first intensity value, and currents of intensity equal to the first intensity value flow through the column conductors, whereby the polarity of the current in the column conductors determines the type of data to be recorded.